The present invention relates to a double-glazed window assembly comprising a preexisting window and a retrofitted assembly including window panelling arranged over the pre-existing window, as well as to a method of forming the double-glazed window, in which the assembly is retrofitted. The double-glazed window assembly may constitute a double-glazed window or part of a multi-glazed window (particularly a triple-glazed window). Double glazing, also known as insulated glazing, involves installation of window panes or panels such that they form two window layers in a window cavity, whereby the resulting window is more resistant to heat transfer, from one side of the window to the other, than if one of the two layers were absent. It is commonly desirable to convert a pre-existing (already installed) standard (single-glazed) window into an in-situ double-glazed window. Carrying out the conversion by way of retrofitting additional window panelling over the pre-existing window is often more cost-effective than replacing the pre-existing window with a double-glazed window. Moreover, the latter mode of conversion is often prohibited by law, particularly where the conversion is to be carried out in a heritage-listed or body corporate building.

Conventional retrofit conversions are expensive and time-consuming. In particular, approximately 90% of windows are not square; that is, vertical and horizontal frame components of the window are not at right angles. Thus, generally speaking, framing for the secondary glaze panelling cannot be prefabricated, instead having to be fabricated on-site, and measurements need to be taken after installation of the framing for the purposes of forming a secondary glaze panel which is appropriately out-of-square to suit. That panel generally must be cut and framed in the factory, necessitating a second visit to the site or oversize dimensioning of the panel in the factory and subsequent cutting thereof to size on-site. According to a first aspect of the present invention, there is provided a double-glazed window assembly comprising:

a pre-existing window installed in a window cavity; and

a retrofitted assembly comprising window panelling, a frame to which the panelling is applied ("the panelling frame"), the panelling frame comprising members extending around a periphery of the panelling ("peripheral frame members"), and a frame fixed around the cavity ("the fixed frame"), wherein the panelling frame is configured to expand and contract with the panelling under changes in temperature of the panelling, and is slidably mounted to the fixed frame so as to move when it expands and contracts.

Preferably, the panelling frame is mounted to the fixed frame so as to be able to float relative thereto in a plane parallel to the panelling.

Preferably, each peripheral frame member is slidably engaged with the fixed frame so as to move axially relative thereto when expanding and contracting.

Preferably, the fixed frame comprises frame members with which the peripheral frame members are slidably engaged ("fixed frame members") whereby the retrofitted assembly includes, adjacent to peripheral edges of the panelling, respective pairs of slidably engaged fixed frame and peripheral frame members, and, in each said pair, one of the members is configured with an axial channel and the other of the members is received by the channel such that the peripheral frame member is axially displaceable relative to the fixed frame member though restrained by the fixed frame member against displacement perpendicular to the panelling. Preferably, in each said pair, the member configured with said channel is arranged such that an entire width of the other member is received within the channel. Preferably, in each said pair, the member configured with said channel comprises parallel flanges defining opposite sides of the channel. Preferably, in at least one said pair, it is the peripheral frame member which is configured with said channel. Preferably, in each said pair, it is the peripheral frame member which is configured with said channel.

Preferably, the assembly comprises resiliency deformable material which is insulative against sound and/or heat transmission and extends around the panelling frame and is compressed between the panelling frame and the fixed frame, the insulative material being arranged such that it is further compressed when the panelling frame expands under an increase in temperature in the panelling and resiles when the panelling frame contracts under a decrease in temperature in the panelling so as to remain in a state of compression between the panelling frame and fixed frame, whereby the material forms between the frames a thermal and/or sound-attenuating barrier which is maintained under thermal expansion and contraction of the panelling. Preferably, the insulative material comprises foam. Preferably, the fixed frame comprises frame members ("fixed frame members") with which the peripheral frame members are slidably engaged whereby the retrofitted assembly includes, adjacent to peripheral edges of the panelling, respective pairs of slidably engaged fixed frame and peripheral frame members, wherein, in each said pair, one of the members is configured with a pair of flanges projecting parallel to the panelling and bounding a recess occupied by a respective length of said material, and the other member is configured with a portion towards which said recess opens and slidably abutting, along the length of the material, an edge of said material, the abutment between said edge and said portion forming a respective said barrier. Preferably, each length of said material is secured within the respective recess. Preferably, in each said pair, said one member includes a web section extending between said flanges, to which the respective length of said material is secured. Preferably, in at least one of said pairs, said one member is a said fixed frame member and said other member is a said peripheral frame member. Preferably, in each of said pairs, said one member is a said fixed frame member and said other member is a said peripheral frame member.

According to a second aspect of the present invention, there is provided a double-glazed window assembly comprising:

a pre-existing window installed in a window cavity; and

a retrofitted assembly comprising a frame structure fitted within the cavity and panelling, comprising at least one window panel, applied to the frame structure, wherein the or each panel is magnetically engaged with the frame structure so as to be held to the frame structure.

Preferably, the or each panel is provided with or comprises magnetic bordering and the frame structure is provided with or comprises opposing magnetic portions arranged to engage said bordering magnetically. Preferably, the magnetic bordering and magnetic portions are in direct abutment. Preferably, magnetic bordering is parallel to a plane in which panelling of said pre-existing window lies. Preferably, the bordering comprises magnetic strips. Preferably, said magnetic portions are defined by magnetic strips applied to said frame structure.

Preferably, the or each panel can be decoupled from the frame structure by application thereto of a load perpendicular to the panel sufficient to overcome the magnetic engagement between the panel and frame structure.

Preferably, assembly of said second aspect accords with said first aspect and said window panelling is defined by said window panel(s) and said frame structure comprises said panelling frame.

Preferably, said window panelling is defined by said window panel(s) and said frame structure comprises said panelling frame, and, in each said pair, the member configured with a said pair of flanges is said fixed frame member, the member configured with a portion towards which said recess opens thus being said peripheral frame member, said portion comprises a web section of the peripheral frame member, and the peripheral frame member includes, projecting from said web section, opposed portions between which said flanges are received such that they form with the opposed portions a sliding fit permitting axial displacement of the peripheral frame member relative to the fixed frame member, and a respective one of the connection portions is defined by or applied to one of said opposed portions which faces away from a plane in which the panelling of the pre-existing window lies.

Preferably, the panelling frame comprises frame members having a coefficient of thermal expansion the same as or similar to that of the panelling whereby the expansion and contraction of the panelling frame comprises thermal expansion and contraction. Alternatively, the panelling frame may comprise frame members, e.g. elastomeric frame members, which are configured to deform elastically under loads exerted on them by the panelling as the panelling expands or contracts, whereby the expansion and contraction of the panelling frame is not thermal.

Preferably, corners of the panelling frame are defined by abutting or adjacent ends of respective pairs of said peripheral frame members, the abutting or adjacent ends of each pair of peripheral frame members being uncoupled interconnected. Preferably, the abutting or adjacent ends of each pair of peripheral frame members are configured with mating mitres. Preferably, the peripheral frame members are configured with slots and the abutting or adjacent ends of each of said pairs of peripheral frame members are interconnected via a respective corner joiner received by the slots with which those peripheral frame members are configured. In a preferred embodiment of the invention, the panelling includes or consists of a pair of adjacent panels and the panelling frame includes at least one intermediate frame member to which adjacent edges of the adjacent panels are secured therealong, an end of the or each intermediate frame member preferably being connected to an end of a respective said peripheral frame member. Preferably, said end of the or each intermediate frame member and the end of the respective peripheral frame member to which the end is connected preferably each being bevelled, whereby the connected peripheral and intermediate frame member ends together form a mitre. Preferably, the or each intermediate frame member and the respective peripheral frame member to the end of which said end of that intermediate frame member is connected are configured with slots and the connected ends are interconnected via a respective corner joiner received by those slots.

In that embodiment, preferably the panelling frame includes two said intermediate frame members adjacent each other, to each of which a respective one of said adjacent edges is secured therealong, and those intermediate frame members are coupled by a joiner opposed sections of which are received in channels thereof whereby each of them is coupled to the other in a manner permitting axial movement of either of the intermediate frame members relative to the other during expansion and contraction of a said panel. The panels in said pair of adjacent panels may be arranged side-by-side, whereby the adjacent intermediate frame members extend generally vertically. Alternatively, the panels in said pair of adjacent panels may be arranged one above the other, whereby the adjacent intermediate frame members extend generally horizontally. Preferably, the joiner coupling the adjacent intermediate members includes a body portion, defining said opposed sections, a portion which extends from the body portion and between the adjacent intermediate frame members so as to project therefrom in a direction away from a plane in which the panelling of the pre-existing window lies, and, supported from that portion, an upwardly projecting portion defining a fence arranged to retain an upper one of the panels which are arranged one above the other, at a lower edge thereof, when that panel has been released from the panelling frame. In a preferred embodiment of the invention, the panelling comprises a pair of adjacent panels and the panelling frame includes at least one intermediate frame member which is coupled to the peripheral frame members and to which adjacent edges of the adjacent panels are secured therealong.

The fixed frame may comprise members formed from metal. The metal may be aluminium, copper or brass.

Preferably, the frame structure or panelling frame comprises members formed from plastic.

Preferably, the panelling is formed from plastic. The plastic may, for example, be acrylonitrile styrene acrylate (ASA).

The assembly may define a double-glazed window. Alternatively, it may form part of a triple-glazed window.

According to a third aspect of the present invention, there is provided a method of forming a double-glazed window assembly as defined above, comprising:

on the basis of dimensions of the cavity where the fixed frame is to be installed: fabricating sections of appropriate length to form members of the fixed frame ("fixed frame members"); and

fabricating members of the panelling frame ("panelling frame members"); securing at least one of the fixed frame members in position in the cavity; and with the panelling frame members arranged to form the panelling frame and applied to the other ones of the fixed frame members, effecting engagement between the panelling frame and the secured fixed frame member(s) and securing said other ones of the fixed frame members in position in the cavity,

wherein the panelling is applied to the panelling frame after the panelling frame has been formed.

Preferably, fabrication of said sections of appropriate length to form the fixed frame members comprises cutting those members from at least one elongate member.

Preferably, fabrication of the panelling frame members comprises cutting those members from at least one elongate member. Preferably, the fixed frame members comprise members which extend along a top, bottom, left side and right side of the panelling frame and said other ones of the fixed frame members comprise the members extending along the top or bottom and along the left and right sides. In one embodiment of the invention, said other ones of the fixed frame members comprise the members extending along the top and the left and right sides. In another embodiment of the invention, the fixed frame members comprise members which extend along a top, bottom, left side and right side of the panelling frame and said other ones of the fixed frame members comprise the members extending along the top and bottom and along the left or right side. Preferably, the panelling is applied to the panelling frame before the slidable mounting of the panelling frame to the fixed frame is effected.

Preferably, the panelling is and/or the panelling frame members are prefabricated offsite at a manufacturing facility.

According to a fourth aspect of the present invention, there is provided the panelling for a window assembly as defined above. According to a fifth aspect of the present invention, there is provided the panelling frame or frame structure for a window assembly as defined above. The invention will now be described, by way of non-limiting example only, with reference to the accompanying drawings, which are briefly described below.

Figure 1 is a perspective view showing details of a window reveal defining a window cavity or opening, a pre-existing window in the cavity and an assembly according to a preferred embodiment of the invention retrofitted in the cavity such that the pre-existing window and assembly define a double-glazed window;

Figure 2 is a perspective view showing detail A marked in Figure 1 ; Figure 3 shows rear, side elevation and bottom views of a panel of the assembly shown in Figure 2;

Figure 4 is an exploded perspective cutaway view showing slidably interengaging members of a fixed frame and panelling frame of the assembly shown in Figure 1;

Figure 5A shows the cross-sectional configuration of the aforementioned panelling frame member;

Figure 5B shows the cross-sectional configuration of the aforementioned fixed frame member;

Figures 6A and 6B are a front elevation view and cross-sectional view, respectively, showing how fixed and panelling frame members slidably interengage in the assembly shown in Figure 1 and a thermal and/or acoustic seal between the members formed by a length of foam tape (Figure 6B being a view of section A-A marked in Figure 6A);

Figures 7A and 7B are are a front elevation view and and cross-sectional side elevation - Si - view, respectively, showing details of the panelling frame and panel applied to that frame (Figure 7B being a view of section A- A marked in Figure 7A);

Figure 8 is a perspective exploded cutaway view showing details of the panelling frame and panel, including interengageable magnetic strips via which the panel attaches to the panelling frame;

Figure 9A is a perspective view of an assembly according to a preferred embodiment of the invention installable over the pre-existing window in the cavity such that the window and assembly together define a double-glazed window;

Figure 9B is a perspective view of the assembly shown in Figure 9A, wherein the top right window panel has been slid to the left to overlap the top left window panel; Figures 10A and 10B are a detail front elevation view and a cross-sectional side elevation view, respectively, showing panels and part of the panelling frame of the assembly shown in Figures 9 A and 9B (Figure 10B being a view of section A- A marked in Figure 9B);

Figure 11A and 11B are cross-sectional views of joiner members of the assembly shown in Figures 9A and 9B;

Figure 11C is a cross-sectional view showing slidably interengaging members of an uppermost horizontal fixed frame member and panelling frame member of the assembly shown in Figures 9A and 9B;

Figure 12 is a partially exploded perspective view showing details of part of the assembly shown in Figures 9A and 9B;

Figure 13 shows the cross-sectional configuration of a panelling frame member which can be used as an alternative to that shown in Figure 4, without departure from the invention;

Figure 14 is a perspective view of a corner piece for joining adjacent perpendicular panelling frame members having the cross-sectional configuration shown in Figure 13; and

Figure 15 shows such adjacent perpendicular panelling frame members joined via the corner piece.

Shown in Figure 1 is a double-glazed window 100 formed in a window reveal 1 defining a cavity in a building. The double-glazed window 100 comprises a pre-existing window, comprising a window pane or panel 3, and an assembly 10 retrofitted in the cavity, the double-glazed window 100 comprising two window layers, one of which is defined by a window panel 20 in the assembly 10 and the other of which is defined by the pre-existing panel 3. The building in which the window 100 is formed may be, for example, a high rise or body corporate building, or a building which is heritage-listed.

Referring to Figure 2, the retrofitted assembly 10 comprises a fixed frame 30 secured around the inside perimeter of the reveal 1, the fixed frame 30 comprising fixed frame members 31, each of those members consisting of a length of extruded section (which is preferably metal, such as aluminium, copper or brass) and secured against a laterally inner face of a respective one of the members making up the reveal 1, and a panelling frame 50, to which the panelling 20 is applied (in a manner which will be described later) and which is configured to expand and contract in-plane with the panelling under changes in temperature in the panelling, the panelling frame 50 comprising members 51 ("peripheral frame members"), extending around the periphery of the panelling 20, each of which is formed from a length of extruded section and is slidably engaged with a respective one of the fixed frame members 31, the slidable engagement between the fixed frame 30 and panelling frame 50 permitting the latter to expand and contract (with the in-plane thermal expansion and contraction of the panel 20) but precluding out-of-plane movement of the frame 50 and thus the panel 20 applied to it.

Figures 4, 5A and 5B show the configurations of the fixed frame members 31 and peripheral frame members 51 in greater detail. Each fixed frame member 31 comprises a web 32, spaced apart flanges 33A and 33B projecting from and perpendicular to the web 32, and a further flange 34 which also projects from and perpendicular to the web 32. As can best be seen at Figure 5B, flange 33A projects from one of the laterally outer edges of the web 32 and flange 34 from the other, whereas flange 33B projects from part of the web intermediate its edges and has the same width (i.e. extent of projection from the web 32) as the flange 33A, that width being greater than the width of the flange 34. The flanges 33A and 33B and a section of the web 32 extending therebetween define a recess 35 in which sound-attenuating and thermally insulative material is to be inserted before or during installation of the assembly 10, as will be described in further detail later. Each peripheral panelling frame member 51 as can best be seen at Figure 5 A, has a stepped web 52, comprising a first web section 52A, a second web section 52B extending from an end of, and perpendicular to, the section 52A, and a third web section 52C extending from an end of, and perpendicular to, the section 52B. The member 51 further comprises a flange 53 extending from a laterally outer end of, and perpendicular to, the web section 52A, and a flange 54 extending from a laterally outer end of, and perpendicular to, the web section 52C. Referring now to Figures 6 A and 6B, the members 31 and 51 are dimensioned such that, in each pair of interengaged members 31, 51 (whether they be a top or bottom horizontal pair of such members or either of the side vertical pairs of such members), the flanges 33A, 33B fit between the flange 53 and web section 52B (between which a channel is defined), whereby to form a substantially size-for-size sliding fit therewith, and a laterally outer face of the flange 34 abuts a laterally inner face of the flange 54 such that there is formed a sliding fit also between the flanges 34 and 54 (whereby defined also between the flanges 53 and 54 of each member 51 is a channel, the channel receiving and transversely trapping a respective one of the members 31 slidably engaged with the member 51). As can be seen in Figure 6B, the members 31 and 51 are dimensioned such that, if the member 31 is inserted fully in the member 51, the distal ends of the flanges 33A and 33B slidably abut the web section 52A and the distal end of the flange 34 slidably abuts the web section 52C, and the distal ends of the flanges 53 and 54 are flush with the face of the web 32 opposite to that from which the flanges 33A, 33B and 34 project. A length of foam tape 40, before the member 31 is slidably coupled to the respective member 51, is inserted into the cavity 35 and an axial face 41 thereof bonded to the web 32 via adhesive pre-applied to the face 41 (which may be exposed by peeling a backing strip off the foam tape 40 before it is inserted into the recess 35). The broken line shown in Figure 6B shows the cross- sectional configuration of the tape 40 before the member 31 to which it is applied is coupled to the respective member 51, and it will be clear that in that configuration, the tape 40 projects beyond the distal ends of the flanges 33 A and 33B; when the members 31 and 51 are coupled, the web 32 and web section 52A compress the tape 40 therebetween. The tape 40, when the member 31 is fully received in the member 51, assumes the cross-sectional configuration shown by the double-line hatching between the flanges 33 A and 33B in Figure 6B. Because the attenuating/insulative material which the strip 40 comprises is resiliently compressible, it will remain in contact with the web section 52A even if it separates from the distal ends of the flanges 33A and 33B, as a result of misalignment between the interengaged members 31 and 51 (typically resulting from a face in the window reveal to which the former is fixed not being true) or thermal contraction of the panelling 20 and panelling frame under a bias urging it towards its uncompressed configuration shown by the broken lines, whereby the acoustic and/or thermal seal formed by the abutment between the material 40 and member 51 is preserved.

Referring now to Figure 3, the panel 20 forms part of a panel unit 25, which unit additionally comprises magnetic strips 21, each of which is applied to a main face of the panel 20 adjacent to a respective edge thereof so as to extend along that edge, and plastic edging, bordering or framing strips 26 each of which is applied to the opposite main face of the panel 20 adjacent a respective edge of the panel so as to extend along that edge (the strips 26 thus assuming, around the perimeter of the face to which they are applied, a configuration which is identical to that shown in the front view in Figure 3). Each magnetic strip 21 comprises extruded isotropic magnetic profile and non-woven acrylic pressure- sensitive tape laminated with the magnetic profile. Each framing strip 26 comprises a length of extruded plastic section and non-woven acrylic pressure-sensitive tape laminated with the plastic section. Adhesive on the tape applied to each of strips 21 and 26, via which the respective strip is secured to the panel 20, may be exposed by peeling a backing strip from the respective strip. It is via the magnetic strips 21 that the panel 20 is mounted (releasably) to the panelling frame 50. To this end, referring to Figures 7A, 7B and 8, each of the peripheral frame members 51 is provided with a magnetic strip 56 complementary to a respective one the strips 21, the magnetic strip 56 being attached (again preferably via adhesive pre-applied to the strip 56 and exposed by removal therefrom of a peel-off backing strip) to the exterior face of web section 52B. Each magnetic strip 56, like each strip 21, comprises extruded isotropic magnetic profile and non-woven acrylic pressure-sensitive tape laminated with the magnetic profile. Adhesive on the tape applied to each of strips 56, via which the respective strip is secured to the respective peripheral frame member 51, may be exposed by peeling a backing strip from the respective strip. The strips 56 applied to the panelling frame members 51 thus form a square or rectangle having the same dimensions as that formed by the strips 21 whereby placement of the strips 21 against the strips 56 causes magnetic interengagement between the strips 56 and 21, such that the panel 20 is mounted to the panelling frame 50. The strips 21 and 56 can expand and contract with the panels 20 and frame members 51 respectively, as can the strips 26, the expansion and contraction of the panels 20 and members 51 being due to changes in temperature therein. Just as the compressed lengths of material 40 provide an acoustic and/or thermal barrier between the perimeter frame 50 and fixed frame 30, the interengaging magnetic strips 21 and 56 provide an acoustic and/or thermal barrier between the panel 20 and the panelling frame 30. When the panel 20 is mounted to the panelling frame 30, each edge thereof abuts the web section 52C of a respective one of the peripheral panelling frame members 51, as can best be seen at Figure 7B. The web section 52C of the lower horizontal member 51 of the frame 50, shown in that drawing, advantageously, defines a shelf on which the panel 20 is supported. Advantageously, owing to the application of the magnetic strips to the panel 20 being direct, whereby the strips 21 are adhered to the rear main face of the panel 20, misalignment of those strips, causing the barrier of which they form a part to be unsatisfactory or unreliable, can be avoided. The abutment or close adjacency between the panel edges and respective web sections 52C gives rise to an aesthetic, uniform finish around the exposed/visible junction between the panel unit 25 and panelling frame 50. The panel unit 25 can be released from the respective perimeter frame to which it is applied by applying to the panel 21 thereof a load sufficient to overcome the magnetic attraction between the magnetic strips on the perimeter frame and panel (which load may, for example, be applied by pulling on one or more suction cups which have been pressed against the panel 21 to engage to that panel by suction).

Fabrication and installation of the assembly 10 so as to form the window 100 will now be described.

The interior dimensions of the window reveal 1 are measured, whereby the appropriate length of each fixed frame member 31 is determined, and the fixed frame members 31 are duly cut, in the appropriate lengths, from a length of extruded section.

The interior dimensions of the reveal 1 also dictate what will be the horizontal and vertical dimensions of the panelling frame 50, and, more particularly, the length of each peripheral frame member 51, which is duly cut, in the appropriate length, from a length of extruded section. The dimensions of the panelling frame 50 are set such that, at at least one of the top and bottom ends of that frame and at least one of the left and right ends of that frame, there is a clearance between the respective panelling frame member 51 and the fixed frame member 31 with which that member is slidably engaged (i.e. the extreme condition, between the interegaged members, shown in Figure 6B is not realised), such that expansion resulting from a temperature increase in panel 20/frame 50 is permitted, both vertically and horizontally.

Referring to Figure 7A, each member 51 is, at each end thereof, bevelled such that that end and the end of an adjacent member 51 abutting it together form a mitre at a respective corner of the frame 50 when assembled. A jig may be used to arrange the members 51 such that they form a rectangle to which the panel unit 25 is to be applied. The abutting ends of the members 51 so arranged are secured together by ultrasonic welding, solvent welding or adhesive. After the members 51 have been cut in the appropriate lengths, the respective magnetic strips 56 are attached to them - either before or after the members 51 are connected end-to-end.

The aforementioned reveal dimensions also dictate the vertical and horizontal dimensions of the panel 20, which is duly cut, in the appropriate size, from a sheet of acrylic (which is latent and sound-deadening), the strips 21 and 26 thereafter being attached to form the panel unit 25.

Installation of the assembly 10 commences with fixing of the lower horizontal fixed frame member 31 against the upper face of the lower horizontal member of the window reveal 1, by driving screws through the section of the web 32 extending between the flanges 34 and 33B and into that member. The length of foam tape 40 for the lower horizontal fixed frame member 31 is, either before or after that member is so fixed, secured in the recess 35 of that member, in the manner previously described. The panelling frame members 51 are arranged end-to-end in a plane to form the aforementioned rectangle, which generally defines the periphery of the panelling frame 50, and secured together at the rectangle corners by the ultrasonic or solvent welding or adhesive as previously described, and the left, right and upper fixed frame members 31, in the recesses 35 of which the respective lengths of foam tape 40 are secured (in the manner previously described), are slidably coupled to the left, right and upper panelling frame members 51 respectively, and are temporarily secured to the respective panelling frame members 51 (e.g. via masking tape), each pair of thus-coupled members 31, 51, together with the respective length of tape 40, forming the configuration shown in Figure 6B. Next, the lower panelling frame member 51 in the assembly comprising the end-to-end interconnected panelling frame members 51 and the left, right and upper fixed frame members 31 (secured to them) is positioned adjacent the already installed lower fixed frame member 31 and that assembly thence tilted upwardly such that the coupling between the lower fixed frame member 31 and the lower panelling frame member 51 (as shown in Figure 6B) is effected and the pairs of slidably coupled members 31, 51 temporarily secured together are arranged in the window reveal/cavity generally at the positions they will occupy when the installation is complete. Thereafter, screws are inserted through respective holes (not shown), preformed through the web sections 52C at spaced positions therealong, and through the respective portions of the webs 32, extending between the flanges 34 and 33B, facing those holes, into the adjacent reveal/cavity member, such that the left, right and upper fixed frame members are secured in position against the left, right and upper reveal/cavity members respectively, the holes being sufficiently large to permit the heads of the screws to pass therethrough so that, when each screw is driven fully home, the head thereof is received against/adjacent the respective web 32. The holes in web sections 52C are then appropriately occluded, either via respective grommets inserted into them or via respective lengths of extruded plastic strip secured over the web sections 52C, e.g. by adhesive pre- applied to those lengths (which may be exposed by peeling respective backing strips therefrom). The temporary interconnections between the panelling frame 50 and the left, right and upper fixed frame members 31 are then removed. The fixed frame 30 and panelling frame 50, slidably/floatably coupled to it, are thus assembled and installed. Finally, the panel unit 25 is lifted into the cavity/reveal such that the magnetic strips 21 thereof engage the strips 56 applied to the panelling frame members 51.

It is possible, without departure from the invention, instead for each chamfered end of each of the panelling frame members 51 not to be fixed to the chamfered end of the adjacent member 51 abutting it (with which end it forms a mitre), in which case the engagement of each member 51 with the respective fixed frame member 31 to which it is slidably coupled and the abutment between that member 51 and the respective pair of members 51 extending substantially perpendicular to it together preclude the members 51 from decoupling from the fixed frame 30.

Without departure from the invention, the panelling frame members may instead have the cross-sectional configuration shown in Figure 13 and the interconnections between the aforementioned ends thereof instead be effected via corner pieces one of which is shown in Figure 14. The alternatively configured panelling frame member 5 has a cross-sectional configuration identical to that of the panelling frame members 51 except that it includes opposed rib portions 52' and 53', projecting laterally inwardly from web section 52B and flange 53 respectively and spaced from the web section 52A such that the web section 52B, flange 53, rib portions 52', 53' and web section 52a define a slot 60. The mitred ends of the panelling frame members 5Γ at each corner of the rectangle in which the members 5 are arranged are coupled via a respective corner piece 70, one of perpendicular arms 71 of which is received snugly into the slot 60 of one of those members 5 and the other of which arms 71 is received into the slot 60 of the other member 5Γ, as shown in Figure 15. The corner piece 70 may be made from the same material as the members 5Γ. The adjacent perpendicular members 5Γ can be held together purely by frictional engagement between them and the respective corner piece 70 when received in the slots 60, or instead adhesive or solvent can be applied between each arm 71 and the respective member 5 which receives that arm, such that the corner piece 70 is adhered or solvent- welded, respectively, to the members 5 . Advantageously, the corner pieces 70 enable the members 5 Γ to be arranged at right angles in a precise manner, and thence fixed together, without any need for a jig.

The panelling in a retrofitted assembly embodying the invention may instead comprise plural window panels. Shown in Figures 9A and 9B is an assembly 10' installable in a window cavity/reveal of the kind previously described with reference to Figure 1, in respect of which assembly like reference numerals are used to refer to like features. The assembly 10' comprises a fixed frame 30' comprising, at each of the left and right lateral sides thereof, upright fixed frame members 31, an upper horizontal fixed frame member 3 , extending between top ends of the upright members 31 and configured with a downwardly projecting flange that will be described in further detail later, and a lower horizontal fixed frame member 31 extending between bottom ends of the upright members and having the same configuration as the lower horizontal fixed frame member 31 of the fixed frame 30. The assembly 10' comprises four panel units 25' - two side-by- side lower panel units and two side-by- side upper panel units. Each panel unit 25', like the panel unit 25, has plastic edging, bordering or framing strips 26 around its periphery on its front/exposed side and magnetic strips around its periphery on its enclosed/rear side.

The panelling frame 50' of the assembly 10' comprises peripheral frame members 51, to each of which a respective magnetic strip 56 is applied, each strip 56 being interengaged with a respective strip 21 on a respective panel edge which lies on the panelling perimeter.

Referring to Figure 12, the panelling frame 50' includes, in addition to peripheral members 51, intermediate members 55 which support respective panel edges that do not lie on a perimeter of the panelling and to which are applied magnetic strips 56, each of those strips being interengaged with a respective strip 21 on a respective panel edge which does not lie on the panelling perimeter. Each of the intermediate members 55 has the same cross-sectional configuration as the members 51. The assembly 10' includes joiner pieces 58, each having a cross-sectional configuration as shown in Figure 1 IB, and a joiner piece 58', having a cross-sectional configuration as shown in Figure 11 A, which pieces may be formed from extruded section, each comprising a rib 59 having a rectangular hollow cross-sectional profile. Each of the joiners 58 consists solely of the rib 59, whereas the joiner 58' comprises the rib 59 and a section 58A which connects to an upright wall/face of the rib 59, the section 58A comprising a first portion 58B, projecting horizontally outwardly from the wall/face, a second portion 58C, projecting upwardly from a distal end of the first portion 58B, a third portion 58D, at an intermediate position along/up the second portion 58C and extending horizontally inwardly therefrom, and a fourth portion 58E, at an intermediate position along the first portion 58C and extending upwardly therefrom to connect to the third portion 58D (thereby supporting it). The sections 58C and 58D will be described in further detail later. Referring again to Figure 12, the ribs 59 are passed into elongate recesses or channels 57 (see Figure 5A) of back-to-back ones of the intermediate frame members 55, thus slidably coupling them together. More specifically, the back-to-back intermediate members 55 defining an upper upright pair 55A of intermediate members are slidably interconnected by a joiner piece 58 received in the elongate recesses 57 of those intermediate members which open towards each other, and the back-to-back intermediate members 55 defining a lower upright pair 55A' of intermediate members are slidably interconnected by a joiner piece 58 received in the elongate recesses 57 of those intermediate members which open towards each other. The back-to-back intermediate members 55 defining a horizontal pair 55B of intermediate members are slidably interconnected by the joiner 58', specifically by the rib 59 thereof, which rib is received in the elongate recesses 57 of those intermediate members. The back-to-back intermediate members 55 defining a horizontal pair 55B' of intermediate members are also slidably interconnected by the joiner 58', specifically by the rib 59 thereof, which rib is, likewise, received in the elongate recesses 57 of those intermediate members; see also Figure 10B.

A jig may be used to arrange the respective members 51 and 55 such that they form a rectangle to which a respective one of the panel units 25' is to be applied. Owing to the ends of the members 51 and 55 being bevelled, mitre junctions are formed by each of the ends of those members and an end of an adjacent one of those members abutting it and extending perpendicular to it. The abutting ends in each pair of abutting ends are secured together by ultrasonic welding, solvent welding or adhesive.

It is possible, without departure from the invention, instead for each chamfered end of each of the frame members 51 in each rectangle not to be fixed to the chamfered end of the adjacent member 55 abutting it. Without departure from the invention, the panelling frame members in each rectangle may, like those in the single window panel embodiment described above, instead have the cross- sectional configuration shown in Figure 13, i.e. be constituted by members 51755', and the interconnections between the aforementioned ends thereof instead effected via corner pieces 70, in the same manner as described in respect of the members 5 in the single window panel embodiment with reference to Figure 15.

It will be clear that the panelling frame 50' comprises plural perimeter frames, each of which comprises the peripheral and intermediate frame members 51/51' and 55/55' which surround a respective one of the panel units 25', and supports that panel unit 25', and is configured to expand and contract, in the plane of the panel 20' of that panel unit, with the panel 20', as a result of temperature changes in the panel 20' (and that perimeter frame itself). There are, for the purposes of permitting the expansion, clearances between the peripheral panelling frame members 51 and fixed frame members 31 as described above in relation to the first embodiment. Lengths of foam tape 40 are, before the fixed frame members 31 are slidably coupled to the respective members 51, inserted into the cavities/channels 35 in the fixed frame members and axial faces 41 thereof bonded to the web 32 via adhesive pre-applied to the face 41 (which may be exposed by peeling a backing strip off the foam tape 40 before it is inserted into the recess 35), in exactly the same manner as described in respect of the assembly 10, such that the same kind of acoustic and/or thermal seal as that described in respect of the assembly 10 is formed between the interengaging members 31 and 51 in the assembly 10'. Referring again to Figure 10B, the web section 52C in the uppermost member 55 in each of the pairs 55B and 55B' of horizontal members aligns with and abuts the portion 58D of the joiner piece 58', such that sections 52C and portion 58D together form a shelf. Any one of the panel units 25' can be released from the respective perimeter frame to which it is applied by applying to the panel 21 ' thereof a load sufficient to overcome the magnetic attraction between the magnetic strips on the perimeter frame and panel (which load may, for example, be applied by pulling on one or more suction cups which have been pressed against the panel 21 ' to engage to that panel by suction). Either of the upper panel units 25' can, when so released, be slid along the shelf. More particularly, referring to Figure 9B, in which the right-hand upper panel unit 25' in Figures 9 A and 10A is shown to be so released, the released panel unit 25' can be slid along the shelf whereby to overlap the panel unit 25' beside which it was positioned before being released (the left-hand upper panel unit 25' in Figures 9 A and 10A), the shelf having sufficient width to support the two overlapping panel units 25', and the portion 58C serves as a fence which precludes the lower edge of the released panel unit 25' from sliding transversely off the shelf, while, referring also to Figure 11C, the flange 3 ID above, likewise serves as a fence, simultaneously precluding the upper edge of the released panel unit 25' from displacing transversely an extent such that it becomes released from the upper fixed frame member 31 ' .

Fabrication and installation of the assembly 10' so as to form the window will now be described.

The interior dimensions of the window reveal 1 are measured, whereby the appropriate length of each of the fixed frame members 31 and 3 is determined, and the fixed frame members 31 and 3 are duly cut, in the appropriate lengths, from lengths of extruded section.

The interior dimensions of the reveal 1 also dictate what will be the horizontal and vertical dimensions of the panelling frame 50', and, more particularly, the length of each of the peripheral frame members 51 and intermediate frame members 55, which is duly cut, in the appropriate length, from a length of extruded section. The dimensions of the panelling frame 50' are set such that, at at least one of the top and bottom ends of that frame and at least one of the left and right ends of that frame, there is a clearance between the respective pair of coaxial panelling frame members 51 and the fixed frame member 31 with which that pair is slidably engaged (i.e. the extreme condition, between the interengaged members, shown in Figure 6 is not realised), such that expansion resulting from a temperature increase in panels 207frame 50' is permitted, both vertically and horizontally.

Although Figures 7A and 7B illustrate details of the perimeter/panelling frame and panel unit 25 of the assembly 10, they are equally illustrative of the details any one of the perimeter frames of the assembly 10' and the panel unit 25' applied to that perimeter frame (either or each of the peripheral frame members 51 shown in that view instead being an intermediate frame member 55, depending on which of the four panel units 25' that drawing is being taken to depict). Thus, each of members 51 and 55 is, at each end thereof, bevelled such that that end and the end of an adjacent member 51/55 abutting it together form a mitre at a respective corner of each of the perimeter frames (surrounding/supporting the respective panel units 25') when assembled. After the members 51 and 55 have been cut in the appropriate lengths, the respective magnetic strips 56 are attached to them. The aforementioned reveal dimensions also dictate the vertical and horizontal dimensions of each of the panels 20', which is duly cut, in the appropriate size, from a sheet of acrylic (which is latent and sound-deadening), the strips 21 and 26 thereafter being attached to form the respective panel unit 25'. Installation of the assembly 10' commences with fixing of the lower horizontal fixed frame member 31 against the upper face of the lower horizontal member of the window reveal 1, by driving screws through the section of the web 32 extending between the flanges 34 and 33B and into that member. The length of foam tape 40 for the lower horizontal fixed frame member 31 is, either before or after that member is so fixed, secured in the recess 35 of that member, in the manner previously described. Thereafter, the peripheral members 51, intermediate members 55 and joiner pieces 58 and 58' of the panelling frame 50' are arranged in the configuration they assume in that frame, and the panelling frame members 51 are temporarily secured together, e.g. via masking tape at the frame corners, and the left and right fixed frame members 31 and upper fixed frame member 3 , in the recesses 35 of which the respective lengths of foam tape 40 are secured (in the manner previously described), are slidably coupled to the left, right and upper panelling frame members 51 respectively, and are temporarily secured to the respective panelling frame members 51 (e.g. via masking tape), in a manner consistent with that described in respect of the assembly 10. Next, the coaxial lower panelling frame members 51 (in the assembly comprising the frame members 51 and 55, the joiner pieces 58 and 58' interconnecting them, and the left and right fixed frame members 31 and upper fixed frame member 3 ) are positioned adjacent the already installed lower fixed frame member 31 and that assembly thence tilted upwardly such that the coupling between the lower fixed frame member 31 and the lower panelling frame members 51 (as shown in Figure 6B) is effected and the slidably coupled members 31, 51 temporarily secured together are arranged in the window reveal/cavity generally at the positions they will occupy when the installation is complete. Thereafter, screws are inserted through respective holes (not shown), preformed through the web sections 52C of the members 51 at spaced positions therealong, and through the respective portions of the webs 32, extending between the flanges 34 and 33B of the members 31 and 31', facing those holes, into the adjacent reveal/cavity member, such that the left, right and upper fixed frame members are secured in position against the left, right and upper reveal/cavity members respectively, the holes being sufficiently large to permit the heads of the screws to pass therethrough so that, when each screw is driven fully home, the head thereof is received against/adjacent the respective web 32. The holes in web sections 52C are then appropriately occluded, either via respective grommets inserted into them or via respective lengths of extruded plastic strip secured over the web sections 52C, e.g. by adhesive pre-applied to those lengths (which may be exposed by peeling respective backing strips therefrom). The temporary interconnections between adjacent ones of the panelling frame members 51 and between those members and the left, right and upper fixed frame members 31 are then removed. The fixed frame 30' and panelling frame 50', slidably/floatably coupled to it, are thus assembled and installed. Finally, the panel units 25' are lifted into the cavity/reveal such that the magnetic strips 21 thereof engage the respective groups of strips 56 applied to the panelling frame members 51 and 55, whereby each unit 25' is supported by a respective pair of perpendicular members 51 and a respective pair of perpendicular members 55.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.